[(i, val) for i, val in enumerate(data) if val % 2 == 0 and i > 3]

Built-in Data Structures

Meaning

Returns a list of (index, value) pairs for elements in `data` that are even and whose index is greater than 3. It combines enumeration, filtering, and tuple construction in a single readable expression.

Primary Function

Data filtering

Communicative Purpose

Select even-valued items occurring after the first three indices and pair them with their indices.

Pattern

[(index, value) for index, value in enumerate(iterable) if value % 2 == 0 and index > 3]

Core Structure

[(..., ...) for ... in enumerate(... ) if ... % 2 == 0 and ... > 3]

Função primária

Data filtering

Propósito comunicativo

Select even-valued items occurring after the first three indices and pair them with their indices.

Situações de gatilho

Data analysis: extracting even numbers after the first four entries; Log processing: selecting even-valued entries beyond the initial header lines

Contextos

General Python code, data analysis scripts, any iterable processing.

Padrão

[(index, value) for index, value in enumerate(iterable) if value % 2 == 0 and index > 3]

Estrutura central

[(..., ...) for ... in enumerate(... ) if ... % 2 == 0 and ... > 3]

Slots de substituição

iterable: iterable of numeric values, index: int ≥ 0, value: numeric

Colocados típicos

often used with list
range
numpy arrays
followed by further processing like sum
map

Substituições comuns

filter with lambda: list(filter(lambda iv: iv[1] % 2 == 0 and iv[0] > 3
enumerate(data)))
or using an explicit for loop

Erros comuns

forgetting that enumerate starts at 0, so i>3 skips the first four elements; applying val%2==0 to non-integers causing TypeError

Similar / contraste

[(val) for i,val in enumerate(data) if val%2==0 and i>3] (values only) ; [i for i,val in enumerate(data) if val%2==0 and i>3] (indices only)

Interferências

Coming from languages like C or Java where manual loop with index is typical; may overlook Python's enumerate convenience.

Família do chunk

list comprehension with enumerate
filter
map

Nuance

If data is not a sequence but an iterator, enumerate will consume it; the list comprehension materializes results; for large data consider a generator expression.

Efeito pragmático

Clarifies intent to pair index with filtered values, avoiding manual index management.

Dica de memória

Think 'enumerate and filter even after index three'.

Nota

Remember that enumerate starts at 0, so i > 3 skips the first four elements. If data is an iterator, enumerate will consume it and the list comprehension materializes results; for large or infinite iterables consider a generator expression to avoid building the whole list in memory.

Upgrade path

Use a generator expression for lazy evaluation: ((i, val) for i, val in enumerate(data) if val % 2 == 0 and i > 3)

Frequência: HighFormulaicidade: Semi-fixedTipo de construção: list comprehension with enumerate and filterPrioridade de aquisição: Active recallPrioridade de output: BothTag de espaçamento: Medium-termIdioma?: Sim

Examples

numbers = [5, 12, 7, 8, 3, 10, 4] result = [(i, v) for i, v in enumerate(numbers) if v % 2 == 0 and i > 3] print(result) # [(5, 10), (6, 4)]

data = list(range(20)) even_after_three = [(i, val) for i, val in enumerate(data) if val % 2 == 0 and i > 3] print(even_after_three) # [(4, 4), (6, 6), (8, 8), (10, 10), (12, 12), (14, 14), (16, 16), (18, 18)]

data = [10, 15, 20, 25, 30, 35] filtered = [(i, v) for i, v in enumerate(data) if v % 2 == 0 and i > 3] print(filtered) # [(4, 30)]